Poliovirus receptor inhibition in breast cancer cells induces antitumor immunity via T cell activation

Radiotherapy (RT) is a commonly used treatment option for patients with cancer because it can effectively control tumor growth and kill tumor cells. However, the impact of RT goes beyond direct tumor cell killing because it can change the tumor microenvironment by altering surrounding tissues and infiltrating cells and modulating the expression of immune checkpoints. Poliovirus receptor (PVR, cluster of differentiation (CD)155), a member of the nectin-like molecule family, is overexpressed in many human cancers. However, its role in the tumor growth and T-cell immune responses of triple-negative breast cancer (TNBC) remains unclear. In the present study, we observe that radiation exposure increases PVR expression in MDA-MB-231 and BT549 cells. Silencing PVR not only inhibited the proliferation of breast cancer cells but also significantly enhanced the cytotoxicity of cytotoxic T lymphocytes (CTLs) compared with the control or RT groups. Treatment of T cells with PVR decreased CD8+ T cells, increased CD4+ T cells, and induced PVR ligands such as T cell immunoreceptor with immunoglobulin and ITIM domain, CD226, and CD96. However, after treatment with PVR, CTL responses decreased and secretion of interferon-γ, tumor necrosis factor-α, interleukin (IL)-2, IL-6, and IL-10 was significantly inhibited. In contrast, PVR knockdown increased the production of these cytokines, illustrating the immunosuppressive function of PVR. Suppression of PVR using an anti-PVR antibody inhibited 4T1 tumor growth by increasing immune cell infiltration. These results provide new insights into the role of PVR in TNBC and highlight its potential as a target for T cell-mediated immunotherapy in breast cancer.

JNC-1043, a Novel Podophyllotoxin Derivative, Exerts Anticancer Drug and Radiosensitizer Effects in Colorectal Cancer Cells

The objective of this study was to determine whether (5S)-5-(4-benzyloxy-3,5-dimethoxy-phenyl)-5,9-dihydro-8H-furo [3’,4’:6,7] naphtho [2,3-d] [1,3]dioxol-6-one (JNC-1043), which is a novel chemical derivative of β-apopicropodophyllin, acts as a novel potential anticancer reagent and radiosensitizer in colorectal cancer (CRC) cells. Firstly, we used MTT assays to assess whether JNC-1043 could inhibit the cell proliferation of HCT116 and DLD-1 cells. The IC50 values of these cell lines were calculated as 114.5 and 157 nM, respectively, at 72 h of treatment. Using doses approximating the IC50 values, we tested whether JNC-1043 had a radiosensitizing effect in the CRC cell lines. Clonogenic assays revealed that the dose-enhancement ratios (DER) of HCT116 and DLD-1 cells were 1.53 and 1.25, respectively. Cell-counting assays showed that the combination of JNC-1043 and γ-ionizing radiation (IR) enhanced cell death. Treatment with JNC-1043 or IR alone induced cell death by 50~60%, whereas the combination of JNC-1043 and IR increased this cell death by more than 20~30%. Annexin V-propidium iodide assays showed that the combination of JNC-1043 and IR increased apoptosis by more 30~40% compared to that induced by JNC-1043 or IR alone. DCFDA- and MitoSOX-based assays revealed that mitochondrial ROS production was enhanced by the combination of JNC-1043 and IR. Finally, we found that suppression of ROS by N-acetylcysteine (NAC) blocked the apoptotic cell death induced by the combination of JNC-1043 and IR. The xenograft model also indicated that the combination of JNC-1043 and IR increased apoptotic cell death in tumor mass. These results collectively suggest that JNC-1043 acts as a radiosensitizer and exerts anticancer effects against CRC cells by promoting apoptosis mediated by mitochondrial ROS.

Receptor interacting protein 1 knockdown induces cell death in liver cancer by suppressing STAT3/ATR activation in a p53-dependent manner

The survival and death of eukaryotic cells are tightly controlled by a variety of proteins in response to the cellular environment. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a receptor-interacting Ser/Thr kinase that has recently been reported as an important regulator of cell survival, apoptosis, and necroptosis; however, its role in liver cancer remains unclear. In this study, we examined the effect of siRNA-mediated RIPK1 knockdown on the survival and death of liver cancer cells. Treatment with siRIPK1 decreased the growth rate of liver cancer cells and increased apoptotic, but not necrotic cell death, which was higher in wild-type p53 (wt-p53) cells than in mutant-type p53 (mt-p53) cells. In addition, RIPK1 knockdown increased p53 expression and G1 phase arrest in wt-p53 cells. Although suppressing p53 did not alter RIPK1 expression, it did attenuate siRIPK1-induced cell death. Interestingly, RIPK1 knockdown also increased the generation of reactive oxygen species and DNA damage by inhibiting signal transduced and activator of transcription 3 (STAT3) and ATM and RAD3-related (ATR) in wt-p53 cells but not in mt-p53 cells. Moreover, STAT3 or ATR inhibition in p53 mutant cells restored siRIPK1-mediated cell death. Together, the results of this study suggest that RIPK1 suppression induces apoptotic cell death by inhibiting the STAT3/ATR axis in a p53-dependent manner. Furthermore, these findings suggest that RIPK1, alone or in combination, may be a promising target for treating liver cancer.

Abstract 6061: Novel β-Apopicropodophyllin derivative, JNC-1043, exerts anti-cancer and radiosensitizing effects

In this study, we reported novel anti-cancer drug candidate, JNC-1043{(5S)-5-(4-Benzyloxy-3,5-dimethoxy-phenyl)-5,9-dihydro-8H-furo[3',4':6,7] naphtho[2,3-d][1,3]dioxol-6-one}, synthesized from β-Apopicropodophyllin. Firstly, we analyzed anti-cancer effect of JNC-1043. We performed MTT assay to detect IC50 values on several cancer cells - breast, lung, pancreatic, blood, gastric, colorectal cancers. In these experiments, 0.1~1 μM IC50 values of JNC-1043 were calculated, and JNC-1043 treatments induced activation of caspase-3 and -8. Additionally, effective values of pharmacokinetic parameters in male rats and 2 weeks Dose Rate Finding (DRF) of JNC-1043 also detected. This result showed JNC-1043 is a promising anti-cancer candidate. Next, we tested whether radiosensitizing effect of JNC-1043. Each IC50 values of DLD-1 and HCT116 cell lines were calculated as 0.157, 0.1145, respectively. Cell counting assays were performed and then showed combination of JNC-1043 and γ-ionizing radiation (IR) enhanced cell death. JNC-1043 only- or IR only-treatment induced cell death by 50~60%, respectively, while combination of JNC-1043 and IR increased more 20~30% cell death than those of JNC-1043 only- or IR only-treatment in both cell lines. Clonogenic assay also performed, and then dose enhancement ratios (DER) of DLD-1 and HCT116 were calculated as 1.40, 1.53, respectively. Apoptosis also was detected with Annexin V-Propidium iodide assay. Combination of JNC-1043 and IR increased apoptosis more 30~40% than those of JNC-1043 only- or IR only-treatment. DCFDA-based assay also were performed to indicate ROS production was enhanced in combination of JNC-1043 and IR. In vivo xenograft experiment, combination of JNC-1043 and IR reduced tumor sizes less 50% and increased apoptosis more 30~40% than those of JNC-1043 only- or IR only-treatment. These results implied anti-cancer and radiosensitizing effect of JNC-1043 resulted from promotion of apoptosis via enhancement of ROS production.

Citation Format: Jong Kuk Park, A-Ram Kang, Jin-Hee Kwon, Jong-Ryoo Choi, Jie-Young Song, Sang-Gu Hwang. Novel β-Apopicropodophyllin derivative, JNC-1043, exerts anti-cancer and radiosensitizing effects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6061.

A novel function of HRP-3 in regulating cell cycle progression via the HDAC-E2F1-Cyclin E pathway in lung cancer

To improve the poor survival rate of lung cancer patients, we investigated the role of HDGF‐related protein 3 (HRP‐3) as a potential biomarker for lung cancer. The expression of endogenous HRP‐3 in human lung cancer tissues and xenograft tumor models is indicative of its clinical relevance in lung cancer. Additionally, we demonstrated that HRP‐3 directly binds to the E2F1 promoter on chromatin. Interestingly, HRP‐3 depletion in A549 cells impedes the binding of HRP‐3 to the E2F1 promoter; this in turn hampers the interaction between Histone H3/H4 and HDAC1/2 on the E2F1 promoter, while concomitantly inducing Histone H3/H4 acetylation around the E2F1 promoter. The enhanced Histone H3/H4 acetylation on the E2F1 promoter through HRP‐3 depletion increases the transcription level of E2F1. Furthermore, the increased E2F1 transcription levels lead to the enhanced transcription of Cyclin E, known as the E2F1‐responsive gene, thus inducing S‐phase accumulation. Therefore, our study provides evidence for the utility of HRP‐3 as a biomarker for the prognosis and treatment of lung cancer. Furthermore, we delineated the capacity of HRP‐3 to regulate the E2F1 transcription level via histone deacetylation.

Anti-leukemic Activity of AIU2008 in FLT3-ITD-positive Acute Myeloid Leukemia

BACKGROUND/AIM

FMS-like tyrosine kinase 3 (FLT3) is a class III receptor tyrosine kinase involved in signal transduction underlying survival, proliferation, and differentiation of hematopoietic cells. An internal tandem duplication (ITD) in FLT3 in the juxtamembrane domain is a common mutation causing human acute myeloid leukemia (AML) and activates constitutive signaling.

MATERIALS AND METHODS

We evaluated the novel FLT3 inhibitor 5-(4-fluorophenyl)-N-(naphthalen-1-yl)oxazol-2-amine (AIU2008) for the treatment of AML.

RESULTS

AIU2008 was designed by modifying FLT3 inhibitor 7c, and showed improved anti-leukemic efficacy in FLT3-ITD-positive AML cells. Specifically, AIU2008 inhibited cell growth and apoptotic death. In addition, AIU2008 down-regulated DNA repair genes involved in homologous recombination and non-homologous end joining. It contributed to the synergistic inhibition of AML cell growth in combination treatment with PARP inhibitors.

CONCLUSION

AIU2008 is a promising FLT3 targeting agent, and may be used in combination with PARP inhibitors for the treatment of AML.

Radiation-induced IL-1β expression and secretion promote cancer cell migration/invasion via activation of the NF-κB-RIP1 pathway

Here, we demonstrate that interleukin-1β (IL-1β) contributes to the γ-ionizing radiation (IR)-induced increase of migration/invasion in A549 lung cancer cells, and that this occurs via RIP1 upregulation. We initially observed that the protein expression and secreted concentration of IL-1β were increased upon exposure of A549 cells to IR. We then demonstrated that IR-induced IL-1β is located downstream of the NF-κB-RIP1 signaling pathway. Treatments with siRNA and specific pharmaceutical inhibitors of RIP1 and NF-κB suppressed the IR-induced increases in the protein expression and secreted concentration of IL-1β. IL-1Ra, an antagonist of IL-1β, treatment suppressed the IR-induced epithelial-mesenchymal transition (EMT) and IR-induced invasion/migration in vitro. These results suggest that IL-1β could regulate IR-induced EMT. We also found that IR could induce the expression of IL-1β expression in vivo and that of IL-1 receptor (R) I/II in vitro and in vivo. The IR-induced increases in the protein levels of IL-1 RI/II and IL-1β suggest that an autocrine loop between IL-1β and IL-1 RI/II might play important roles in IR-induced EMT and migration/invasion. Based on these collective results, we propose that IR concomitantly activates NF-κB and RIP1 to trigger the NF-κB-RIP1-IL-1β-IL-1RI/II-EMT pathway, ultimately promoting metastasis.

MKI-1, a Novel Small-Molecule Inhibitor of MASTL, Exerts Antitumor and Radiosensitizer Activities Through PP2A Activation in Breast Cancer

Although MASTL (microtubule-associated serine/threonine kinase-like) is an attractive target for anticancer treatment, MASTL inhibitors with antitumor activity have not yet been reported. In this study, we have presented a novel MASTL inhibitor, MKI-1, identified through in silico screening and in vitro analysis. Our data revealed that MKI-1 exerted antitumor and radiosensitizer activities in in vitro and in vivo models of breast cancer. The mechanism of action of MKI-1 occurred through an increase in PP2A activity, which subsequently decreased the c-Myc protein content in breast cancer cells. Moreover, the activity of MKI-1 in the regulation of MASTL-PP2A was validated in a mouse oocyte model. Our results have demonstrated a new small-molecule inhibitor of MASTL, MKI-1, which exerts antitumor and radiosensitizer activities through PP2A activation in breast cancer in vitro and in vivo.

Abstract 6394: Combined FLT3 and PARP inhibition induces synthetic lethality in non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related deaths worldwide. Fms-like receptor tyrosine kinase 3 (FLT3), a member of class III receptor tyrosine kinase, targeted inhibitors have not been well studied in lung cancer including NSCLC. Since recent studies have been reported that FLT3 inhibitors can suppress DNA repair activities, we investigated the antitumor activities of quizartinib, an FLT3 inhibitor, in NSCLC cells to expand the use of FLT3 inhibitors. Quizartinib inhibited the growth of NSCLC cells in a concentration-dependent manner, and induced DNA damage and reactive oxygen species (ROS) generation in A549 and H1299 cells. We found that quizartinib suppressed DNA damage repair genes through the downregulation of STAT5, resulting in the ‘BRCAness' or ‘DNA-PKness' phenotype in A549 and H1299 cells. As quizartinib-induced ‘BRCAness/DNA-PKness' and poly(ADP-ribose) polymerase inhibitors (PARP) inhibition can induce synthetic lethality, combined treatment with quizartinib and olaparib, a PARP inhibitor, showed synergistic inhibitory proliferation and apoptotic cell death in A549 and H1299 cells compared with either drug alone. Taken together, our findings suggest that quizartinib may be a synthetic lethal partner of PARP inhibitors to enhance therapeutic efficacy in NSCLC cells.

Citation Format: Hwani Ryu, Hyo Jeong Kim, Jie-Young Song, Sang-Gu Hwang, Jiyeon Ahn. Combined FLT3 and PARP inhibition induces synthetic lethality in non-small cell lung cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6394.

Gene expression profiling of glioblastoma cell lines depending on TP53 status after tumor-treating fields (TTFields) treatment

Glioblastoma is frequently associated with TP53 mutation, which is linked to a worse prognosis and response to conventional treatments (chemoradiotherapy). Therefore, targeting TP53 is a promising strategy to overcome this poor therapeutic response. Tumor-treating fields (TTFields) are a recently approved treatment for newly diagnosed glioblastoma, which involves direct application of low-intensity, intermediate-frequency alternating electric fields to the tumor, thereby offering a local tumor-killing effect. However, the influence of TP53 mutation status on the effectiveness of TTFields is controversial. Here, we identified the key gene signatures and pathways associated with TTFields in four glioblastoma cell lines varying in TP53 mutation status using gene profiling and functional annotation. Overall, genes associated with the cell cycle, cell death, and immune response were significantly altered by TTFields regardless of TP53 status. TTFields appeared to exert enhanced anti-cancer effects by altering the immune system in the inflammatory environment and regulating cell cycle- and cell death-related genes, but the precise genes influenced vary according to TP53 status. These results should facilitate detailed mechanistic studies on the molecular basis of TTFields to further develop this modality as combination therapy, which can improve the therapeutic effect and minimize side effects of chemoradiotherapy.

Kinesin light chain 4 as a new target for lung cancer chemoresistance via targeted inhibition of checkpoint kinases in the DNA repair network

The poor therapeutic efficacy of non-small cell lung cancer (NSCLC) is partly attributed to the acquisition of chemoresistance. To investigate the mechanism underlying this resistance, we examined the potential link between kinesin light chain 4 (KLC4), which we have previously reported to be associated with radioresistance in NSCLC, and sensitivity to chemotherapy in human lung cancer cell lines. KLC4 protein levels in lung cancer cells correlated with the degree of chemoresistance to cisplatin treatment. Furthermore, KLC4 silencing enhanced the cytotoxic effect of cisplatin by promoting DNA double-strand breaks and apoptosis. These effects were mediated by interaction with the checkpoint kinase CHK2, as KLC4 knockdown increased CHK2 activation, which was further enhanced in combination with cisplatin treatment. In addition, KLC4 and CHEK2 expression levels showed negative correlation in lung tumor samples from patients, and KLC4 overexpression correlated negatively with survival. Our results indicate a novel link between the KLC4 and CHK2 pathways regulating DNA damage response in chemoresistance, and highlight KLC4 as a candidate for developing lung cancer-specific drugs and customized targeted molecular therapy.

Tumor-Treating Fields Induce RAW264.7 Macrophage Activation Via NK-κB/MAPK Signaling Pathways

Objective:

Tumor-treating fields are currently used to successfully treat various cancers; however, the specific pathways associated with its efficacy remain unknown in the immune responses. Here, we evaluated tumor-treating fields–mediated initiation of the macrophage-specific immune response.

Materials and Methods:

We subjected RAW 264.7 mouse macrophages to clinically relevant levels of tumor-treating fields (0.9 V/cm, 150 kHz) and evaluated alterations in cytokine expression and release, as well as cell viability. Additionally, we investigated the status of immunomodulatory pathways to determine their roles in tumor-treating fields–mediated immune activation.

Results and Discussion:

Our results indicated that tumor-treating fields treatment at 0.9 V/cm decreased cell viability and increased cytokine messenger RNA/protein levels, as well as levels of nitric oxide and reactive oxygen species, relative to controls. The levels of tumor necrosis factor α, interleukin 1β, and interleukin 6 were markedly increased in tumor-treating fields–treated RAW 264.7 cells cocultured with 4T1 murine mammary carcinoma cells compared with those in 4T1 or RAW 264.7 cells with or without tumor-treating fields treatment. Moreover, the viability of 4T1 cells treated with the conditioned medium of tumor-treating fields–stimulated RAW 264.7 cells decreased, indicating that macrophage activation by tumor-treating fields effectively killed the tumor cells. Moreover, tumor-treating fields treatment activated the nuclear factor κB and mitogen-activated protein kinase pathways involved in immunomodulatory signaling.

Conclusion:

These results provide critical insights into the mechanisms through which tumor-treating fields affect macrophage-specific immune responses and the efficacy of this method for cancer treatment.

5-Fluorouracil as a Tumor-Treating Field-Sensitizer in Colon Cancer Therapy

Colorectal cancer (CRC) is a major cause of mortality that can be treated effectively with chemotherapy and radiotherapy, although resistance to these therapeutic modalities often occurs. Tumor-treating fields (TTFields) can block tumor growth by selectively impairing tumor cell division. In this study, we investigated the mechanism by which 5-fluorouracil (5-FU) sensitizes tumor cells to TTFields. Human HCT116 and SW480 CRC cells were treated with 5-FU and/or TTFields, and characterized in vitro in terms of cell viability, apoptosis through reactive oxygen species production, autophagy, and metastatic potentials. The biological effects of 5-FU and/or TTFields were studied via positron emission tomography and computed tomography on xenograft tumor growth and were confirmed with organoid models of patients. Our results revealed that combination treatment with 5-FU and TTFields increased the efficiency of TTFields therapy in colon cancer cells by downregulating signaling pathways associated with cell proliferation, survival, cell invasion, and migration while upregulating pathways mediating apoptosis and autophagic cell death. The novel mechanistic insights gleaned in this study suggest that combination therapy with TTFields and 5-FU may be effective in treating CRC, although safety and efficacy testing in patients with CRC will need to be performed before this strategy can be implemented clinically for TTF-sensitization.

A new FGFR inhibitor disrupts the TGF-β1-induced fibrotic process

Pulmonary fibrosis (PF) is chronic and irreversible damage to the lung characterized by fibroblast activation and matrix deposition. Although recently approved novel anti‐fibrotic agents can improve the lung function and survival of patients with PF, the overall outcomes remain poor. In this study, a novel imidazopurine compound, 3‐(2‐chloro‐6‐fluorobenzyl)‐1,6,7‐trimethyl‐1H‐imidazo[2,1‐f]purine‐2,4(3H,8H)‐dione (IM‐1918), markedly inhibited transforming growth factor (TGF)‐β‐stimulated reporter activity and reduced the expression of representative fibrotic markers, such as connective tissue growth factor, fibronectin, collagen and α‐smooth muscle actin, on human lung fibroblasts. However, IM‐1918 neither decreased Smad‐2 and Smad‐3 nor affected p38MAPK and JNK. Instead, IM‐1918 reduced Akt and extracellular signal‐regulated kinase 1/2 phosphorylation increased by TGF‐β. Additionally, IM‐1918 inhibited the phosphorylation of fibroblast growth factor receptors 1 and 3. In a bleomycin‐induced murine lung fibrosis model, IM‐1918 profoundly reduced fibrotic areas and decreased collagen and α‐smooth muscle actin accumulation. These results suggest that IM‐1918 can be applied to treat lung fibrosis.

Abstract 287: A novel class III receptor tyrosine kinase inhibitor synergizes with olaparib by inhibition of DNA repair-related genes in non-small cell lung cancer cells

The platelet-derived growth factor receptors (PDGFRs), which are classified with class III receptor tyrosine kinase (RTK) family, play critical roles in cell proliferation, differentiation, and malignancy in various types of human cancers. To develop novel class III RTK inhibitors, dozen novel oxazole amine derivatives were designed and synthesized. Among the synthesized compounds, KM201 showed inhibitory activities of pan-class III RTK by an in vitro kinase activity assay and potent anti-proliferative activities in variety of cancer cell lines including leukemia and solid cancer cells. Genome-wide RNAseq profiling revealed a significant decrease of DNA repair-related genes in non-small cell lung cancer A549 cells treated with KM201. Moreover, KM201-induced DNA damage was detected by H2AX phosphorylation, which led to cell cycle arrest in the G2/M phase. We hypothesized that KM201 in combination with a PARP inhibitor may exhibit synergistic effect on inhibition of proliferation since PARP inhibitors are primarily effective against cancers with loss-of-function mutations in BRCA1 and BRCA2. Combination of KM201 and olaparib (a PARP inhibitor) markedly more effective in anti-proliferation and apoptotic cell death in A549 and H1299 cells harboring wild type BRCA1/2, compared with either drug alone. Our results show that the novel class III RTK inhibitor KM201 inhibits proliferation of leukemia and solid tumor cells by potentiating DNA damage and exerts synergistic cytotoxicity in combination with olaparib. Further detailed studies could help to investigate the full potential of KM201 as a class III RTK inhibitor and a combination adjuvant of PARP inhibitors.

Citation Format: Hwani Ryu, Jie-young Song, Sang-Gu Hwang, Jiyeon Ahn. A novel class III receptor tyrosine kinase inhibitor synergizes with olaparib by inhibition of DNA repair-related genes in non-small cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 287.

Abstract 1973: RIP1 and its signaling network regulate radiation-induced modification of cancer microenvironment

Radiotherapy is the principal treatment method for inducing cell death in various cancer types such as lung cancer; however, this therapeutics is frequently associated with occurrence of resistance such as recurrences or metastasis due to recent studies that radiotherapy might promote cancer progression and metastasis. Recurrences or metastasis is major cause of treatment failure of cancer, but its intra-/inter-cellular molecular mechanisms was not identified clearly yet due to the fact that genetic characteristics of cancer are extremely diverse according to individuals. Therefore, the objective of this study is to investige the modifications of intracellular signaling/genetic profiling in ionizing radiation (IR)-irradiated microenvironment of non-small-cell lung cancer (NSCLC), and to provide new therapeutic target for treatment of metastatic cancer. Previously, we have studied that IR treatment increased migration and invasion via induction of epithelial-mesenchymal transition (EMT) in A549 cells. With the same system, we found the increase of expression level of receptor interacting protein 1 (RIP1) in IR-treated A549, and this increased expression of RIP1 is associated with IR-induced EMT induction in vitro. NCI-H460 and A549 overexpressing RIP1 was established, and these transfectants also showed increased of migration and invasion via EMT induction. Signaling analyses indicated activation of EGFR-Src-STAT3 pathway is required for the EMT induction, and RIP1 exerts effect on this pathway resulting in activation of EGFR- RIP1-Src-STAT3 pathway. The down-regulation of RIP1 expression by treatment of siRNA, pharmaceutical inhibitor for RIP1 kinase, or dominant negative mutant of the kinase suppressed not only the activation of EGFR-RIP1-Src-STAT3, but also the EMT induction; this suggests that RIP1 might be one of key molecules in IR-induced migration/invasion. Additionally, DNA profiling analyses of RIP1-overexpressed NCI-H460 and A549 indicated that IL-1β is the most prominent over-expressed gene in common. IR treatment also stimulated IL-1β expression and its upstream NF-κB activation via increase of RIP1 followed by induction of EMT and cancer invasion/migration. Supernatants of stable cells including secreted IL-1β treatment promoted invasion/migration of NCI-H460 and A549 cells via EMT induced by activation of EGFR- RIP1-Src-STAT3 pathway. Taken together, our present results imply that RIP1 signals through EGFR- RIP1-Src-STAT3 axis and also through RIP1-NF-κB-IL-1β pathway. This also suggest that these two pathways are connected with common molecule, RIP1, which is novel signaling pathway and activations of these two pathways contribute to new autocrine signaling involving IL-1β secretion; therefore, RIP1 has a role as a novel biomarker as well as a molecular target for suppressing lung cancer metastasis.

Citation Format: Jeong Hyun Cho, Jung Lim Kim, Hong-Duck Um, Sang-Gu Hwang, EunAh Lee, Sang-Churl Oh, Jong Kuk Park. RIP1 and its signaling network regulate radiation-induced modification of cancer microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1973.

Radiosensitizing Effect of Novel Phenylpyrimidine Derivatives on Human Lung Cancer Cells via Cell Cycle Perturbation

Radiotherapy is one of the most common treatments for cancer, but radioresistance and injury to normal tissue are considered major obstacles to successful radiotherapy. Thus, there is an urgent need to develop radiosensitizers to improve the therapeutic outcomes of radiotherapy in cancer patients. Our previous efforts to identify novel radiosensitizers, using high-throughput screening targeting p53 and Nrf2 revealed a promising N-phenylpyrimidin-2-amine (PPA) lead compound. In the present study, 17 derivatives of this lead compound were examined, and it was found that 4-(4-fluorophenyl)-N-(4-nitrophenyl)-6-phenylpyrimidin-2-amine (PPA5), 4-((4-(4-fluorophenyl)pyrimidin-2-yl)amino)-3-methoxy-N-methyl -benzamide (PPA13), 4-((4-(4-fluorophenyl)pyrimidin-2-yl)amino)benzenesulfonamide (PPA14), 4-((4-(2-chlorophenyl)pyrimidin-2-yl)amino)benzenesulfonamide (PPA15), and 4-((4-(2-chlorophenyl)pyrimidin-2-yl)amino)-N-methylbenzamide (PPA17) inhibited cell viability by more than 50%, with a marked increase in the proportion of cells arrested at the G₂/M phase of cell cycle. Among these compounds, PPA15 markedly increased the sub-G₁ cell population and increased the levels of cyclin B1 and the phosphorylation levels of cyclin-dependent kinase (CDK) 1. Combined treatment with radiation and PPA14 or PPA15 significantly decreased clonogenic survival. An in vitro kinase assay revealed that PPA15 inhibited multiple CDKs involved in cell cycle regulation. Compared with drug or radiation treatment alone, combined treatment with PPA15 and radiation resulted in the suppression of A549 tumor growth in mice by 59.5% and 52.7%, respectively. Treatment with PPA15 alone directly inhibited tumor growth by 25.7%. These findings suggest that the novel pan CDK inhibitor, PPA15, may be a promising treatment to improve the effectiveness of radiotherapy for the treatment of cancer. SIGNIFICANCE STATEMENT: Several inhibitors of CDK have been successfully evaluated in combination with other chemotherapeutics in clinical trials, but negative side effects have partially restricted their clinical use. In this study, we identified a novel pan-CDK inhibitor to increase radiosensitivity, and we hope this work will encourage the development of promising small-molecule radiosensitizers.

Inhibition of Karyopherin-α2 Augments Radiation-Induced Cell Death by Perturbing BRCA1-Mediated DNA Repair

Ionizing radiation (IR) has been widely used in the treatment of cancer. Radiation-induced DNA damage triggers the DNA damage response (DDR), which can confer radioresistance and early local recurrence by activating DNA repair pathways. Since karyopherin-α2 (KPNA2), playing an important role in nucleocytoplasmic transport, was significantly increased by IR in our previous study, we aimed to determine the function of KPNA2 with regard to DDR. Exposure to radiation upregulated KPNA2 expression in human colorectal cancer HT29 and HCT116 cells and breast carcinoma MDA-MB-231 cells together with the increased expression of DNA repair protein BRCA1. The knockdown of KPNA2 effectively increased apoptotic cell death via inhibition of BRCA1 nuclear import following IR. Therefore, we propose that KPNA2 is a potential target for overcoming radioresistance via interruption to DDR.

β-Apopicropodophyllin functions as a radiosensitizer targeting ER stress in non-small cell lung cancer

AIMS

In this study, we examined whether β-apopicropodophyllin (APP) could act as a radiosensitizer in non-small cell lung cancer (NSCLC) cells.

MAIN METHODS

The in vitro radiosensitizing activity of APP was demonstrated with clonogenic assay, immunoblotting, Annexin V-Propidium iodide (PI) assay, BrdU incorporation, detection of mitochondrial ROS/intracellular of H₂O₂, mitochondrial membrane potential detection, and performing of isolation of mitochondrial and cytosolic fractions. The in vivo radiosensitizing activity of APP was determined in xenografted mice with co-treatment of APP and IR based on measurement of tumor volumes and apoptotic cell death.

KEY FINDINGS

The results of a clonogenic assay indicated that a combination of APP and γ-ionizing radiation (IR) inhibits cell growth and increases cell death in NSCLC cells. Several signal transduction pathways were examined for their potential involvement in the apparent radiosensitization effect of APP, as assessed by immunoblotting analyses and mitochondrial potential determination in vitro. Treatment of NCI-H460 cells with 15 nM APP and NCI-H1299 cells with 10 nM APP yielded dose-enhancement ratios of 1.44 and 1.24, respectively. Enhanced ER stress, disrupted mitochondrial membrane potential, and increased reactive oxygen species (ROS) were observed in cells co-treated with APP and IR, and this was followed by the cytosolic release of cytochrome c and consequent activation of caspase-3 and -9. Notably, inhibition of JNK, which prevents caspase activation, blocked the APP/IR-induced activations of ER stress and apoptotic cell death. In NCI-H460 or NCI-H1299 cell-xenografted mice, APP/IR treatment delayed the time it took tumors to reach a threshold size by 22.38 and 16.83 days, respectively, compared with controls, to yield enhancement factors of 1.53 and 1.38, respectively.

SIGNIFICANCE

APP has a radiosensitizing function derived from its ability to induce apoptotic cell death via activation of ER stress, disruption of mitochondrial membrane potential, and induction of the caspase pathway.

Functional Biological Activity of Sorafenib as a Tumor-Treating Field Sensitizer for Glioblastoma Therapy

Glioblastoma, the most common primary brain tumor in adults, is an incurable malignancy with poor short-term survival and is typically treated with radiotherapy along with temozolomide. While the development of tumor-treating fields (TTFields), electric fields with alternating low and intermediate intensity has facilitated glioblastoma treatment, clinical outcomes of TTFields are reportedly inconsistent. However, combinatorial administration of chemotherapy with TTFields has proven effective for glioblastoma patients. Sorafenib, an anti-proliferative and apoptogenic agent, is used as first-line treatment for glioblastoma. This study aimed to investigate the effect of sorafenib on TTFields-induced anti-tumor and anti-angiogenesis responses in glioblastoma cells in vitro and in vivo. Sorafenib sensitized glioblastoma cells to TTFields, as evident from significantly decreased post-TTFields cell viability (p < 0.05), and combinatorial treatment with sorafenib and TTFields accelerated apoptosis via reactive oxygen species (ROS) generation, as evident from Poly (ADP-ribose) polymerase (PARP) cleavage. Furthermore, use of sorafenib plus TTFields increased autophagy, as evident from LC3 upregulation and autophagic vacuole formation. Cell cycle markers accumulated, and cells underwent a G2/M arrest, with an increased G0/G1 cell ratio. In addition, the combinatorial treatment significantly inhibited tumor cell motility and invasiveness, and angiogenesis. Our results suggest that combination therapy with sorafenib and TTFields is slightly better than each individual therapy and could potentially be used to treat glioblastoma in clinic, which requires further studies.

PLOD3 promotes lung metastasis via regulation of STAT3

Procollagen-lysine, 2-oxoglutarate 5-dioxygenase (PLOD3), a membrane-bound homodimeric enzyme, hydroxylates lysyl residues in collagen-like peptides; however, its role in lung cancer is unknown. This study aimed to investigate the role of PLOD3 as a pro-metastatic factor and to elucidate the underlying mechanism. First, we experimentally confirmed the release of PLOD3 in circulation in animal models, rendering it a potential serum biomarker for lung cancer in humans. Thereafter, we investigated the effects of PLOD3 overexpression and downregulation on cancer cell invasion and migration in vitro and in vivo, using human lung cancer cell lines and a mouse tumor xenograft model, respectively. Further, PLOD3 levels were determined in lung tissue samples from lung cancer patients. Functional analyses revealed that PLOD3 interacts with STAT3, thereby expressing matrix metalloproteinases (MMP-2 and MMP-9) and with urokinase plasminogen activator (uPA) to enhance tumor metastasis. PLOD3 and the STAT3 pathway were significantly correlated in the metastatic foci of lung cancer patients; PLOD3–STAT3 levels were highly correlated with a poor prognosis. These results indicate that PLOD3 promotes lung cancer metastasis in a RAS-MAP kinase pathway-independent manner. Therefore, secreted PLOD3 serves as a potent inducer of lung cancer metastasis and a potential therapeutic target to enhance survival in lung cancer.

MASTL inhibition promotes mitotic catastrophe through PP2A activation to inhibit cancer growth and radioresistance in breast cancer cells

BACKGROUND

Although MASTL (microtubule-associated serine/threonine kinase-like) is a key mitotic kinase that regulates mitotic progression through the inactivation of tumor suppressor protein phosphatase 2A (PP2A), the antitumor mechanism of MASTL targeting in cancer cells is still unclear.

METHODS

MASTL expression was evaluated by using breast cancer tissue microarrays and public cancer databases. The effects of MASTL depletion with siRNAs were evaluated in various breast cancer cells or normal cells. Various methods, including cell viability, cell cycle, soft agar, immunoblotting, immunofluorescence, PP2A activity, live image, and sphere forming assay, were used in this study.

RESULTS

This study showed the oncosuppressive mechanism of MASTL targeting that promotes mitotic catastrophe through PP2A activation selectively in breast cancer cells. MASTL expression was closely associated with tumor progression and poor prognosis in breast cancer. The depletion of MASTL reduced the oncogenic properties of breast cancer cells with high MASTL expression, but did not affect the viability of non-transformed normal cells with low MASTL expression. With regard to the underlying mechanism, we found that MASTL inhibition caused mitotic catastrophe through PP2A activation in breast cancer cells. Furthermore, MASTL depletion enhanced the radiosensitivity of breast cancer cells with increased PP2A activity. Notably, MASTL depletion dramatically reduced the formation of radioresistant breast cancer stem cells in response to irradiation.

CONCLUSION

Our data suggested that MASTL inhibition promoted mitotic catastrophe through PP2A activation, which led to the inhibition of cancer cell growth and a reversal of radioresistance in breast cancer cells.

Abstract 3197: Beta-Apopicropodophyllin, a derivative of podophyllotoxin, has a function as anticancer drug and radiosenstizer against non-small cell lung cancer cells

We have synthesized new 32 derivatives of podophyllotoxin and screened candidate showed anti-cancer effect. Among these derivatives, we found beta-Apopicropodophyllin (APP) is candidate derivative inducing cell death against non-small cell lung cancer (NSCLC) cell lines: A549, NCI-1299 and NCI-460 (IC50 values =16.9, 13.1 and 17.1 nM, respectively). We also analyzed MOA (mode of action) of APP and found APP induced cell death via various mechanisms. Firstly, APP inhibits the polymerization of microtubule and induces G2/M phase arrest as well as DNA damage. APP treatment induces expressions of mitosis-related proteins, phospho-ATM, γ-H2AX and p21. Next, the intrinsic and extrinsic apoptotic pathways by APP are activated as shown in the activations of caspase-3, -8 and -9. APP also induces pro-apoptotic ER stress signaling pathway as indicated by elevated expression levels of BiP, phospo-eIF2α, CHOP and ATF4. Additionally, APP also showed radiosensitizer function. Combination of APP and gamma-ionizing radiation (IR) enhanced apoptotic cell death of NSCLC cell via amplification of ER stress. Taken together, these results implied APP might be a potent anti-cancer drug candidate inducing microtubule disruption, DNA damage, cell cycle arrest and ER stress.

Citation Format: Ju Yeon Kim, Jeong Hyun Cho, Sang-Gu Hwang, Jie-Young Song, EunAh Lee, Hong-Duck Um, Jong Kuk Park. Beta-Apopicropodophyllin, a derivative of podophyllotoxin, has a function as anticancer drug and radiosenstizer against non-small cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3197.

miR-550a-3-5p acts as a tumor suppressor and reverses BRAF inhibitor resistance through the direct targeting of YAP

Although evidence has emerged to suggest that YAP overexpression is a crucial factor for tumor progression and resistance to targeted drugs in multiple cancers, the miRNA-mediated YAP regulation is still unclear. Here we show that the novel miR-550a-3-5p acts as a tumor suppressor and reverses BRAF inhibitor resistance through the direct targeting of YAP. Our data showed that the miR-550a-3-5p suppressed cell proliferation, metastasis, and tumor sphere formation through the direct inhibition of YAP and its oncogenic pathway in various cancer cell types. In addition, we showed that the YAP signature was associated with poor survival of colon cancer and identified an inverse correlation between miR-550a-3-5p and YAP in colon cancer tissues. Interestingly, this inverse correlation was regulated in a density-dependent manner. Furthermore, high levels of miR-550a-3-5p were associated with a good prognosis of esophageal cancer, which was suggestive of the clinical relevance of miR-550a-3-5p-mediated YAP regulation in multiple cancers. Importantly, we demonstrated that miR-550a-3-5p treatment sensitized vemurafenib-resistant colon and melanoma cells through YAP inhibition with reduced AKT activity. Moreover, the tumor-suppressive activity of miR-550a-3-5p and its sensitization effect for vemurafenib resistance were also observed in tumor xenograft models. Collectively, our data suggest that miR-550a-3-5p acts as a tumor suppressor through the targeting of oncogenic YAP and may be a new therapeutic tool for YAP-mediated BRAF inhibitor resistance in BRAF-mutant cancer cells.

Kinesin light chain-4 depletion induces apoptosis of radioresistant cancer cells by mitochondrial dysfunction via calcium ion influx

Kinesins act as molecular microtubule-dependent motor proteins and have various important cellular functions related to cell division, intracellular transport, and membrane trafficking. However, the function of kinesin light chain 4 (KLC4) in cancer, especially radioresistance, has not been previously described. Thus, we investigated KLC4 function in lung cancer cells and radioresistant R-H460 cells by analyzing alterations in radiosensitivity after gene knockdown with siRNA and by evaluating cellular phenotypes and xenograft tumor growth. KLC4 was upregulated in human lung cancer cell lines. Moreover, in paired clinical specimens of lung cancer patients, KLC4 expression was significantly higher in tumor tissues than in paired adjacent normal tissues. Fluorescence-activated cell sorting (FACS) analysis showed that apoptosis rates and cleaved poly (ADP-ribose) polymerase (PARP) and cleaved caspase-3 levels in KLC4-knockdown lung cancer cells were significantly increased compared with those in control cells. Colony formation decreased as the radiation dose increased in KLC4-knockdown lung cancer cells, demonstrating an essential role for KLC4 in radioresistance. Importantly, KLC4 silencing suppressed tumor growth in an in vivo xenograft model, accompanied by increased apoptosis. Finally, KLC4-knockdown cells exhibited impaired mitochondrial respiration, increased mitochondrial reactive oxygen species production, and enhanced mitochondrial calcium uptake, resulting in mitochondrial dysfunction. Thus, KLC4 as a kinesin superfamily-targeted therapy may represent a novel, effective anticancer strategy, particularly for patients showing radioresistance.

Knockdown of end-binding protein 1 induces apoptosis in radioresistant A549 lung cancer cells via p38 kinase-dependent COX-2 upregulation

The role of end-binding protein 1 (EB1) in lung cancer tumorigenesis and radiotherapy remains poorly understood. In the present study, we observed that EB1 was highly expressed in lung tumor tissues compared with normal non-tumor tissues based on immunohistochemical analysis of lung cancer tissue samples obtained from human tissue microarrays. EB1 was also highly overexpressed in radioresistant lung and cervical cancer cells, which exhibited increased cell death after EB1 silencing. The cytotoxicity induced by EB1 gene knockdown was due to the activation and generation of reactive oxygen species by p38 mitogen-activated protein kinase. Notably, this signaling cascade, however not nuclear factor-κB-mediated signaling, induced the expression of cyclooxygenase-2, a key effector of apoptotic death. Our results provided new molecular evidence supporting the use of EB1 as a novel target in lung cancer therapy, especially in the case of radioresistance.

Dichloroacetate potentiates tamoxifen-induced cell death in breast cancer cells via downregulation of the epidermal growth factor receptor

Metabolic reprogramming in cancer cells has recently been recognized as an essential hallmark of neoplasia. In this context, metabolic alterations represent an attractive therapeutic target, and encouraging results with drugs targeting various metabolic processes have been obtained in preclinical studies. Recently, several studies have suggested that dichloroacetate (DCA), a specific pyruvate dehydrogenase kinase inhibitor, may be a potential anticancer drug in a large number of diverse tumors. However, the precise mechanism is not fully understood, which is important for the use of DCA in cancer treatment. In the present study, we found that DCA sensitized MCF7 breast cancer cells to tamoxifen-induced cell death by decreasing epidermal growth factor receptor (EGFR) expression. The downregulation of EGFR was caused by degradation of the protein. Furthermore, p38 mitogen-activated protein kinase played an important role in DCA/tamoxifen-induced EGFR degradation. Finally, DCA also promoted comparable tamoxifen-induced cell death in tamoxifen-resistant MCF7 cells, which were established by long-term treatment with tamoxifen. In summary, our results suggest that DCA is an attractive potential drug that sensitizes cells to tamoxifen-induced cell death and overcome tamoxifen resistance via downregulation of EGFR expression in breast cancer cells.

Involvement of SULF2 in y-irradiation-induced invasion and resistance of cancer cells by inducing IL-6 expression

Cancer cells that survive radiotherapy often display enhanced invasiveness and resistance to death stimuli. Previous findings have suggested that ionizing radiation (IR) induces such undesirable effects by stimulating the STAT3/Bcl-XL pathway. To identify novel cellular components that mediate these actions of IR, we irradiated lung cancer cells with sublethal doses of y-rays and screened for the induction of IR-responsive genes by microarray analysis. The genes encoding 2 extracellular proteins, SULF2 and IL-6, were found to be upregulated, and these results were confirmed by polymerase chain reactions and western blot analyses. Because the IR-mediated induction of SULF2 was a novel finding, we also confirmed the phenomenon in vivo using xenograft tumors in mice. Analyses of signaling processes revealed that IR induced SULF2 expression via p53, which then promoted IL-6 expression by stabilizing β-catenin, followed by stimulation of the STAT3/Bcl-XL pathway. Consistently, both SULF2 and IL-6 mediated IR-induced invasion and resistance to death stimuli. To investigate whether SULF2 contributes to IR-induced tumor metastasis, we irradiated tumors in mice with sublethal doses of IR. This treatment promoted the entry of tumor cells into the blood stream (intravasation), which was abolished by downregulating SULF2 expression in tumor cells. These results demonstrated that SULF2 can mediate the detrimental effects of IR in vivo. Therefore, SULF2 may be potentially used as a therapeutic and diagnostic target to predict and overcome the malignant effects of IR, particularly in tumors expressing p53 wild-type.

Effects of low-dose irradiation on mice with Escherichia coli-induced sepsis

Although favorable immune responses to low-dose irradiation (LDI) have been observed in normal mice, i.e., a hormesis effect, little is known about the effects of LDI in infectious diseases. In this study, we examined the effects of LDI on mice with sepsis, a severe and often lethal hyperinflammatory response to bacteria. Female C57BL/6 mice were whole-body irradiated with 10cGy 48h before Escherichia coli infection, and survival, bacterial clearance, cytokines, and antioxidants were quantified. LDI pretreatment significantly increased survival from 46.7% in control mice to 75% in mice with sepsis. The bacterial burden was significantly lower in the blood, spleen, and kidney of LDI-treated mice than in those of control septic mice. The levels of pro-inflammatory cytokines, e.g., IL-1β and IL-6, as well as anti-inflammatory IL-10 were markedly reduced in pre-LDI septic mice. Nitric oxide production by peritoneal macrophages was also reduced in pre-LDI septic mice. Immune cells in the spleen increased and Nrf2 and HO-1 were induced in pre-LDI septic mice. LDI stimulates the immune response and minimizes lethality in septic mice via enhanced bacterial clearance and reduced initial proinflammatory responses.

Antihelminthic drug niclosamide inhibits CIP2A and reactivates tumor suppressor protein phosphatase 2A in non-small cell lung cancer cells

Protein phosphatase 2A (PP2A) is a critical tumor suppressor complex responsible for the inactivation of various oncogenes. Recently, PP2A reactivation has emerged asan anticancer strategy. Cancerous inhibitor of protein phosphatase 2A (CIP2A), an endogenous inhibitor of PP2A, is upregulated in many cancer cells, including non-small cell lung cancer (NSCLC) cells. We demonstrated that the antihelminthic drug niclosamide inhibited the expression of CIP2A and reactivated the tumor suppressor PP2A in NSCLC cells. We performed a drug-repurposing screen and identified niclosamide asa CIP2A suppressor in NSCLC cells. Niclosamide inhibited cell proliferation, colony formation, and tumor sphere formation, and induced mitochondrial dysfunction through increased mitochondrial ROS production in NSCLC cells; however, these effects were rescued by CIP2A overexpression, which indicated that the antitumor activity of niclosamide was dependent on CIP2A. We found that niclosamide increased PP2A activity through CIP2A inhibition, which reduced the phosphorylation of several oncogenic proteins. Moreover, we found that a niclosamide analog inhibited CIP2A expression and increased PP2A activity in several types of NSCLC cells. Finally, we showed that other well-known PP2A activators, including forskolin and FTY720, did not inhibit CIP2A and that their activities were not dependent on CIP2A. Collectively, our data suggested that niclosamide effectively suppressed CIP2A expression and subsequently activated PP2A in NSCLC cells. This provided strong evidence for the potential use of niclosamide asa PP2A-activating drug in the clinical treatment of NSCLC.

Abstract 4181: Discovery of a selective small molecule inhibitor of Tankyrase by structure-based screening

The Wnt/β-catenin signaling pathway is critical for colorectal cancer (CRC) development, progression and metastasis. Tankyrase enzymes (TNKS1 and TANKS2), members of the PARP (Poly(ADP-ribose)polymerases) superfamily, PARsylate and target Axin for degradation via ubiquitin-proteasome pathway, leading to accumulation of β-catenin into nucleus. In addition, aberrant YAP/TAZ singling contributes to anticancer drug resistance, but inhibition of TNKS suppresses YAP/TAZ signaling through stabilizing Angiomotin (AMOT). Therefore, inhibition of TNKS has emerged as an attractive strategy for treatment of cancers. To identify potent and selective small molecule inhibitors of TNKS1, a TNKS1-ligand docking was used for computational-based virtual screen of a chemical library containing 1.6 million compounds and 24 virtual hits were further subjected to in vitro evaluation for TNKS1 inhibition. Using an in vitro TNKS1 enzyme assay, we identified a novel pyridine derivative (AZ236106) significantly inhibited TNKS1 enzyme activity in a concentration-dependent manner, but not PARP1/2. Treatment of AZ236106 stabilized Axin, reduced β-catenin in nucleus and downregulated β-catenin target genes in DLD-1 cells harboring adenomatous polyposis coli (APC) mutation. Moreover, we observed that AZ236106 inhibited accumulation of YAP in the nucleus and expression of YAP garget genes. Combination treatment of AZ236106 with either radiation or PLX4032, a BRAF inhibitor, decreased cell proliferation and increased apoptotic cell death in DLD-1 and SK-MEL28 cells, compare to AZ236106, radiation or PLX4032 alone. Our findings suggest that AZ236106 may have therapeutic potential in cancers, and could be further refined for efficacy and safety to develop a lead compound.

Citation Format: Hwani Ryu, Ah-young Kim, Jie-Young Song, Sang-Gu Hwang, Jiyeon Ahn. Discovery of a selective small molecule inhibitor of Tankyrase by structure-based screening [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4181. doi:10.1158/1538-7445.AM2017-4181

Abstract 5853: Peroxiredoxin I-targeted AMRI-59 has a role of radiosensitizer by promoting induction of ROS/γH2AX/caspase pathway and suppression of ERK

We have identified AMRI-59, one of small molecule, is specific pharmaceutical inhibitor of peroxiredoxin (PRX) I enzyme activity in our previous study. In this study, we tried to prove whether AMRI-59 has role of radiosensitizer against non-small cell lung cancer cells - NCI-H460 and NCI-H1299. The radiosensitizer effects of AMRI-59 were tested with clonogenic assays. The intracellular mechanism underlying this effect was determined by performing immunoblotting and measuring ROS generation, mitochondrial potential and cell death. The radiosensitizer activity of AMRI-59 in vivo was tested in nude mice by treating with AMRI-59 and IR, and measuring tumor volume and assessing apoptosis. Dose-enhancement ratios of 30 μM AMRI-59 in NCI-H460 and NCI-H1299 are 1.57 or 3.38, respectively. Combination with AMRI-59 and IR also increased the production of ROS and disruption of mitochondrial potential via enhancement of PrxI oxidation, which subsequently induced one of DNA damage markers - phospho-γH2AX, and suppressed phosphorylation of ERK, and, finally, activated caspase-3. Notably, inhibition of ROS production prevented ERK suppression, and inhibition of ERK in addition of combination with AMRI-59 and IR increased caspase activation and apoptosis. In a xenograft assay, combination with AMRI-59 and IR delayed tumor growth by 11.4 days compared with controls, yielding an enhancement factor of 1.48. Collectively, these results indicate that AMRI-59 functions as a Prx I - targeted radiosensitizer by induction of apoptosis through activation of a ROS/γH2AX/caspase pathway and suppression of ERK.

Citation Format: Wan Gi Hong, Jeong Hyun Cho, Ju Yeon Kim, EunAh Lee, Sang-Gu Hwang, Tong-Shin Chang, Hong-Duck Um, Jong Kuk Park. Peroxiredoxin I-targeted AMRI-59 has a role of radiosensitizer by promoting induction of ROS/γH2AX/caspase pathway and suppression of ERK [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5853. doi:10.1158/1538-7445.AM2017-5853

The p53/p21 Complex Regulates Cancer Cell Invasion and Apoptosis by Targeting Bcl-2 Family Proteins

The tumor suppressor p53 binds prosurvival Bcl-2 family proteins such as Bcl-w and Bcl-X_L to liberate Bax, which in turn exerts proapoptotic or anti-invasive functions depending on stress context. On the basis of our previous finding that p53 interacts with p21, we investigated the possible involvement of p21 in these functions. Here, we report that although p53 can bind Bcl-w alone, it requires p21 to liberate Bax to suppress cell invasion and promote cell death. p21 bound Bcl-w, forming a p53/p21/Bcl-w complex in a manner that maintained all pairwise p53/p21, p21/Bcl-w, and p53/Bcl-w interactions. This allowed Bax liberation from the complex. Accordingly, a p53 derivative incapable of binding p21 failed to mediate radiotherapy-induced tumor cell death in mice. Bcl-X_L also served as a target of the cooperative action of p53 and p21. Overall, our findings indicate that the p53/p21 complex rather than p53 itself regulates cell invasion and death by targeting Bcl-2 proteins. We propose that the p53/p21 complex is a functional unit that acts on multiple cell components, providing a new foundation for understanding the tumor-suppressing functions of p53 and p21. Cancer Res; 77(11); 3092-100. ©2017 AACR.

STAT3-survivin signaling mediates a poor response to radiotherapy in HER2-positive breast cancers

Although radiotherapy resistance is associated with locoregional recurrence and distant metastasis in breast cancers, clinically relevant molecular markers and critical signaling pathways of radioresistant breast cancer are yet to be defined. Herein, we show that HER2-STAT3-survivin regulation is associated with radiotherapy resistance in HER2-positive breast cancers. Depletion of HER2 by siRNA sensitized HER2-positive breast cancer cells to irradiation by decreasing STAT3 activity and survivin, a STAT3 target gene, expression in HER2-positive breast cancer cells. Furthermore, inhibition of STAT3 activation or depletion of survivin also sensitized HER2-positive breast cancer cells to irradiation, suggesting that the HER2-STAT3-survivin axis is a key pathway in radiotherapy resistance of HER2-positive breast cancer cells. In addition, our clinical analysis demonstrated the association between HER2-positive breast cancers and radiotherapy resistance. Notably, we found that increased expression of phosphorylated STAT3, STAT3, and survivin correlated with a poor response to radiotherapy in HER2-positive breast cancer tissues. These findings suggest that the HER2-STAT3-survivin axis might serve as a predictive marker and therapeutic target to overcome radiotherapy resistance in HER2-positive breast cancers.

Radiotherapy diagnostic biomarkers in radioresistant human H460 lung cancer stem-like cells

Tumor cell radioresistance is a major contributor to radiotherapy failure, highlighting the importance of identifying predictive biomarkers for radioresistance. In this work, we established a radioresistant H460 (RR-H460) cell line from parental radiosensitive H460 lung cancer cells by exposure to fractionated radiation. The radiation-resistant, anti-apoptotic phenotype of RR-H460 cell lines was confirmed by their enhanced clonogenic survival and increased expression of the radioresistance genes Hsp90 and Her-3. RR-H460 cells displayed characteristics of cancer stem-like cells (CSCs), including induction of the surface marker CD44 and stem cell markers Nanog, Oct4, and Sox2. RR-H460 cells also exhibited sphere formation and malignant behavior, further supporting a CSC phenotype. Using proteomic analyses, we identified 8 proteins that were up-regulated in RR-H460 CSC lines and therefore potentially involved in radioresistance and CSC-related biological processes. Notably, 4 of these—PAI-2, NOMO2, KLC4, and PLOD3—have not been previously linked to radioresistance. Depletion of these individual genes sensitized RR-H460 cells to radiotoxicity and additively enhancing radiation-induced apoptosis. Our findings suggest the possibility of integrating molecular targeted therapy with radiotherapy as a strategy for resolving the radioresistance of lung tumors.

Fbxw7β, E3 ubiquitin ligase, negative regulation of primary myoblast differentiation, proliferation and migration

Satellite cells attached to skeletal muscle fibers play a crucial role in skeletal muscle regeneration. During regeneration, the satellite cells proliferate, migrate to the damaged region, and fuse to each other. Although it is important to determine the cellular mechanisms controlling myoblast behavior, their regulators are not well understood. In this study, we evaluated the roles of Fbxw7 in primary myoblasts and determined its potential as a therapeutic target for muscle disease. We originally found that Fbxw7β, one of the E3 ubiquitin ligase Fbxw7 subtypes, negatively regulates differentiation, proliferation and migration of myoblasts and satellite cells on muscle fiber. However, these phenomena were not observed in myoblasts expressing a dominant-negative, F-box deleted Fbxw7β, mutant. Our results suggest that myoblast differentiation potential and muscle regeneration can be regulated by Fbxw7β.

Selective inhibition of histone deacetylase 2 induces p53-dependent survivin downregulation through MDM2 proteasomal degradation

In the present study, we found that selective inhibition of histone deacetylase 2 (HDAC2) with small inhibitory RNA (siRNA) induced survivin downregulation in a p53-dependent manner. Interestingly, suberoylanilide hydroxamic acid (SAHA) or knockdown of HDAC2 induced downregulation of Mdm2, a negative regulator of p53, at the protein level. SAHA and/or HDAC2 siRNA increased Mdm2 ubiquitination, and MG132, an inhibitor of proteosome function, prevented HDAC2 inhibition-induced degradation of Mdm2. Clinically, the mRNA levels of HDAC2 and survivin were prominently overexpressed in lung cancer patients compared to normal lung tissues. Silencing of HDAC2 enhanced the cell death caused by ionizing radiation in lung cancer cells. Collectively, our results indicate that selective inhibition of HDAC2 causes survivin downregulation through activation of p53, which is mediated by downregulation of Mdm2. They further suggest that HDAC2 may exert a dominant effect on lung cancer cell survival by sustaining Mdm2-survivin levels.

Abstract 1241: Podophyllotoxin acetate (PA) as an anti-cancer drug candidate regulates various malignancy traits of non-small cell lung cancer

Here, we reported that podophyllotoxin acetate (PA) showed various aniti-cancer effects: induction of several cell death pathways, inhibition of γ-ionizing radiation (IR)-induced cancer invasion, chemo-sensitizer effect with topoisomerase (TOP) inhibitors against non-small cell lung cancer (NSCLC) cell lines as follows. (1) Stimulation of cell death via various mechanisms. First, PA dose-dependently induced cell cycle arrest at G2/M phase, as shown by accumulation of the mitosis-related proteins, p21, survivin and aurora B. This arrest was due to the PA-induced inhibition of microtubule polymerization that related to DNA damage (reflected by accumulation of γ-H2AX) resulting induction of intrinsic/extrinsic damage apoptotic pathways. PA also activated the pro-apoptotic ER stress pathway, as evidenced by increased expression levels of BiP, CHOP, IRE1-a, phospho-PERK, and phospho-JNK. Next, PA induced autophagy that reflected the expression of beclin-1, Atg3, Atg5 and Atg7, and the cleavage of LC3. (2) Inhibition of IR-induced cancer invasion. IR increased the invasion/migration of A549 cells, and this effect was decreased by PA treatment that the expressions/activities of matrix metalloprotase (MMP) -2, MMP-9, and vimentin, suggesting that PA could block the IR-induced epithelial-mesenchymal transition (EMT). In this study, we also identified IR-induced new signaling pathway, EGFR - p38/ERK - CREB-1/STAT3 - EMT pathway, that was inhibited by PA. (3) Chemo-sensitizer effect conjugated with TOP inhibitors - etoposide (Eto) and camptothecin (Cpt). Combination Index (CI) values of the combinations showed synergistic effects between PA and topoisomerase inhibitors. Combination with PA and Eto/Cpt promotes disruption of dynamics of actin filaments, which subsequently enhanced apoptotic cell death that accompanied to increased phosphorylation of p38. We also observed these combinations also inhibited activation of CREB-1, synergistically. Therefore, this study indicated that PA functions as a chemosensitizer by enhancing apoptosis through activation of p38/caspases apoptotic axis and suppression of CREB-1.Taken together; these results suggest PA is a new anti-cancer drug candidate that could control several malignancy traits of cancer including uncontrolled cell cycle and IR-induced invasion.

Citation Format: Jeong Hyun Cho, Wan Gi Hong, Sang-Gu Hwang, Hong-Duck Um, Jong Kuk Park. Podophyllotoxin acetate (PA) as an anti-cancer drug candidate regulates various malignancy traits of non-small cell lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1241.

Multipotent neurogenic fate of mesenchymal stem cell is determined by Cdk4-mediated hypophosphorylation of Smad-STAT3

Cyclin-dependent kinase (Cdk) in complex with a corresponding cyclin plays a pivotal role in neurogenic differentiation. In particular, Cdk4 activity acts as a signaling switch to direct human mesenchymal stem cells (MSCs) to neural transdifferentiation. However, the molecular evidence of how Cdk4 activity converts MSCs to neurogenic lineage remains unknown. Here, we found that Cdk4 inhibition in human MSCs enriches the populations of neural stem and progenitor pools rather than differentiated glial and neuronal cell pools. Interestingly, Cdk4 inhibition directly inactivates Smads and subsequently STAT3 signaling by hypophosphorylation, and both Cdk4 and Smads levels are linked during the processes of neural transdifferentiation and differentiation. In summary, our results provide novel molecular evidence in which Cdk4 inhibition leads to directing human MSCs to a multipotent neurogenic fate by inactivating Smads-STAT3 signaling.

Induction of immunogenic cell death by radiation-upregulated karyopherin alpha 2 in vitro

Accumulating evidence suggests the potential for radiation therapy to generate antitumor immune responses against tumor cells by inducing immunogenic cell death and phenotypic changes. We recently found that ionizing radiation upregulated karyopherin α2 (KPNA2) in HT-29 colorectal tumor cells using quantitative proteomic analysis. To determine whether this increased KPNA2 could function as a damage-associated molecular pattern to induce antitumor immune responses, mouse bone-marrow-derived dendritic cells (BMDCs) were treated with KPNA2. KPNA2 enhanced the surface expression of CD40, CD54, CD80, CD86, and MHC class I/II on BMDCs. DCs treated with KPNA2 exhibited increased secretion of pro-inflammatory cytokines such as IL-1β, IL-6, IL-12, IL-23, and TNF-α. Co-culture of CD4(+) T cells and KPNA2-treated DCs resulted in induction of Th1/17 cytokines (IFN-γ and IL-17) and reduction of TGF-β production. Moreover, KPNA2-treated DCs were capable of increasing granzyme B and perforin expression in cytotoxic T lymphocytes. These results demonstrated that radiation-induced dying colorectal cancer cells released considerable amounts of KPNA2 that induce the maturation and activation of DCs for synergistic antitumor effect of radiation.

Chemosensitizing effect of podophyllotoxin acetate on topoisomerase inhibitors leads to synergistic enhancement of lung cancer cell apoptosis

Podophyllotoxin acetate (PA) acts as a radiosensitizer against non-small cell lung cancer (NSCLC) in vitro and in vivo. In this study, we examined its potential role as a chemosensitizer in conjunction with the topoisomerase inhibitors etoposide (Eto) and camptothecin (Cpt). The effects of combinations of PA and Eto/Cpt were examined with CompuSyn software in two NSCLC cell lines, A549 and NCI-H1299. Combination index (CI) values indicated synergistic effects of PA and the topoisomerase inhibitors. The intracellular mechanism underlying synergism was further determined using propidium iodide uptake, immunoblotting and electrophoretic mobility shift assay (EMSA). Combination of PA with Eto/Cpt promoted disruption of the dynamics of actin filaments, leading to subsequent enhancement of apoptotic cell death via induction of caspase-3, -8, and -9, accompanied by increased phosphorylation of p38. Conversely, suppression of p38 phosphorylation blocked the apoptotic effect of the drug combinations. Notably, CREB-1, a transcription factor, was constitutively activated in both cell types, and synergistically inhibited upon combination treatment. Our results collectively indicate that PA functions as a chemosensitizer by enhancing apoptosis through activation of the p38/caspase axis and suppression of CREB-1.

The novel anthraquinone derivative IMP1338 induces death of human cancer cells by p53-independent S and G2/M cell cycle arrest

To identify novel small molecules that induce selective cancer cell death, we screened a chemical library containing 1040 compounds in HT29 colon cancer and CCD18-Co normal colon cells, using a phenotypic cell-based viability assay system with the Cell Counting Kit-8 (CCK-8). We discovered a novel anthraquinone derivative, N-(4-[{(9,10-dioxo-9,10-dihydro-1-anthracenyl)sulfonyl}amino]phenyl)-N-methylacetamide (IMP1338), which was cytotoxic against the human colon cancer cells tested. The MTT cell viability assay showed that treatment with IMP1338 selectively inhibited HCT116, HCT116 p53(-/-), HT29, and A549 cancer cell proliferation compared to that of Beas2B normal epithelial cells. To elucidate the cellular mechanism underlying the cytotoxicity of IMP1338, we examined the effect of IMP1338 on the cell cycle distribution and death of cancer cells. IMP1338 treatment significantly arrested the cell cycle at S and G2/M phases by DNA damage and led to apoptotic cell death, which was determined using FACS analysis with Annexin V/PI double staining. Furthermore, IMP1338 increased caspase-3 cleavage in wild-type p53, p53 knockout HCT116, and HT29 cells as determined using immunoblotting. In addition, IMP1338 markedly induced the phosphorylation of histone H2AX and Chk1 in both cell lines while the combination of 5-fluorouracil (5-FU) and radiation inhibited the viability of HCT116, HCT116 p53(-/-), and HT29 cells compared to 5-FU or radiation alone. Our findings indicated that IMP1338 induced p53-independent cell death through S and G2/M phase arrest as well as DNA damage. These results provide a basis for future investigations assessing the promising anticancer properties of IMP1338.

Proton Irradiation Sensitizes Radioresistant Non-small Cell Lung Cancer Cells by Modulating Epidermal Growth Factor Receptor-mediated DNA Repair

Although proton radiotherapy is effective in treating various types of cancer, little is known on the biological responses triggered by proton irradiation. In the present study, we investigated protein profiles following proton irradiation of non-small cell lung cancer (NSCLC) cells and defined the role of proton-induced epidermal growth factor receptor (EGFR) expression in NSCLC cells. We found that proton irradiation more effectively sensitized NSCLC cells than gamma irradiation did. The expression profiles of radiosensitive and radioresistant NSCLC cells following proton and gamma irradiation were examined using antibody arrays. With regard to proteins, expression of EGFR was the most highly induced by proton irradiation. In addition, we found that EGFR inhibition with gefinitib significantly increased the radiosensitivity of NSCLC cells, and that increased radiosensitivity due to gefinitib was mediated by the suppression of DNA repair in radioresistant NSCLC cells. Thus, our data provide the first evidence that proton irradiation sensitizes radioresistant NSCLC cancer cells by modulating EGFR-mediated DNA repair.

ERp57 modulates STAT3 activity in radioresistant laryngeal cancer cells and serves as a prognostic marker for laryngeal cancer

Although targeting radioresistant tumor cells is essential for enhancing the efficacy of radiotherapy, the signals activated in resistant tumors are still unclear. This study shows that ERp57 contributes to radioresistance of laryngeal cancer by activating STAT3. Increased ERp57 was associated with the radioresistant phenotype of laryngeal cancer cells. Interestingly, increased interaction between ERp57 and STAT3 was observed in radioresistant cells, compared to the control cells. This physical complex is required for the activation of STAT3 in the radioresistant cells. Among STAT3-regulatory genes, Mcl-1 was predominantly regulated by ERp57. Inhibition of STAT3 activity with a chemical inhibitor or siRNA-mediated depletion of Mcl-1 sensitized radioresistant cells to irradiation, suggesting that the ERp57-STAT3-Mcl-1 axis regulates radioresistance of laryngeal cancer cells. Furthermore, we observed a positive correlation between ERp57 and phosphorylated STAT3 or Mcl-1 and in vivo interactions between ERp57 and STAT3 in human laryngeal cancer. Importantly, we also found that increased ERp57-STAT3 complex was associated with poor prognosis in human laryngeal cancer, indicating the prognostic role of ERp57-STAT3 regulation. Overall, our data suggest that ERp57-STAT3 regulation functions in radioresistance of laryngeal cancer, and targeting the ERp57-STAT3 pathway might be important for enhancing the efficacy of radiotherapy in human laryngeal cancer.

IM-412 inhibits the invasion of human breast carcinoma cells by blocking FGFR-mediated signaling

Triple-negative breast cancer (TNBC) is an aggressive cancer with a poor prognosis due to its epithelial‑to-mesenchymal transition (EMT) phenotype. Cancer patients often experience several detrimental effects of cancer treatment, such as chemoresistance, radioresistance and the maintenance of cancer stem cells due to EMT. Thus, EMT signaling is considered to be a valuable therapeutic target for cancer treatment, and its inhibition is being attempted as a new treatment option for TNBC patients. Previously, we showed that 3-(2-chlorobenzyl)-1,7-dimethyl-1H-imidazo[2,1-f]purine‑2,4(3H,8H)-dione (IM-412) inhibits transforming growth factor-β (TGF-β)-induced differentiation of human lung fibroblasts through both Smad-dependent and -independent pathways. In the present study, we examined the inhibitory effect of IM-412 on EMT pathways and invasiveness in TNBC cells since the TGF-β signaling pathway is a typical signaling pathway that functions in EMT. IM-412 not only potently suppressed the migration and invasion of MDA-MB-231 cells, but also lowered the expression of mesenchymal markers and EMT-activating transcription factors in these cells. IM-412 inhibited the activation of several signaling proteins, including Smad2/Smad3, p38MAPK, Akt and JNK, and it also attenuated the phosphorylation of FGFR1 and FGFR3. Collectively, our findings suggest that the synthetic compound IM-412 suppressed the EMT process in MDA-MB-231 cells and thereby effectively inhibited the migration and invasion of these cancer cells. Thus, IM-412 could serve as a novel therapeutic agent for malignant cancers.